Gaseous electric discharge device



y ,1 G. GAIDIES EFAL 2,251,046

- GASEOUS ELECTRIC DISCHARGE DEVICE Original Filed April 24, 1930 INVENTORS WW I ATTORNEY Patented July 29, 1941 GASEOUS ELECTRIC DISCHARGE DEVICE Georg Gaidies, Berlin-Pankow, and Marcello Pirani, Berlin-Wilmersdorf, Germany, assignors to General Electric Company, a corporation of New York Original application April 24, 1930, Serial No.

Divided and this application April 20,

1932, Serial No. 606,366. In Germany June 29,

Claims. (01. 176-126) The present invention relates to gaseous electric discharge devices generally and methods of operating the same and more particularly the invention relates to electrodes useful in electric discharge devices generally.

It is the object of this invention to provide electrodes for electric discharge devices, which electrodes are extremely rugged in structure, have a long operating life, are free from sputtering, do not require a separate heating circuit, will function by being connected directly to the current supply circuit of the discharge device, will permit greater current densities at the electron emitting electrodes of electric discharge devices than any electrodes heretofore proposed, and in the case of gaseous discharge devices do not consume or clean up the gaseous content whether of rare gas or common gas, or mixtures thereof, thus extending the life of such devices considerably beyond that of previous devices. Further objects and advantages of the invention will be apparent from the following particular description and from the claims. 1

In accordance with these objects the invention comprises an electrode made of a compact body of desired shape, being electron emitting oxide material poorly conducting in its cold state, and

a metal body supporting, as by covering, in part, the surface of the compact oxide body. The surface of the compact oxide body exposed is small in comparison to the mass of said body, hence the electrode material is not easily sputtered. A thick compactmass of the oxide material may be made by pressing and sintering the pulverized form of said material. The metal body partially covering the surface of the oxide body has a large surface as compared to its mass and this is quickly heated and brought to a. glow under the influence of the discharge. The parts of the oxide body adjacent the metal covering are strongly heated by radiation and conduction of the heat of the metal covering and in this heated condition send out a continuous stream of electrons to support the discharge. By reason of the small surface of the oxide body exposed, as compared to the mass of said body, a large reservoir of electron emitting material is provided so that a strong steady stream of electrons is sent forth which maintains the are at greater constancy than an oxide coated metal shell electrode. Because of the greater constancy of the discharge and the reduction in sputtered electrode material, due to the small surface exposed, consumption of the gas filling is avoided and it thus is now possible for the first time to operate electric discharge devices filled with common gases such as nitrogen for more than several hundred hours, whereas heretofore replenishing of the gaseous content of such common gas tubes. every few seconds or minutes has been necessary.

The metal part of the electrode, used for heating the electron emitting oxide part of the electrode, may be attached to said oxide part in any desired manner.- It may be a-coil wound around the oxide part, or it may be a wire web enclosing said oxide part. A manner of attaching the metal part to the oxide part possessing many advantages is by placing one or more wires in such position in the oxide part, which in this case has a block or slab shape, that the ends of said wire extend beyond the surface of the oxide part. In this case the wires are connected directly to the current circuit of the discharge device. The oxide body-enclosing parts of the wires preventsthe radiation of heat from said parts so that the end parts of the wires extending beyond the surface of the oxide part of the electrode are quickly and strongly heated by the current from the discharge device circuit. This naturally facilitates the starting of the discharge.

If the starting voltage of the discharge device is not suflicient to bring the metal part of the electrode to a glowingcondition, as 220 volts or less, a higher voltage can be connected to the electrodes to facilitate starting. In this case the metal part of the electrode is likewise maintained at a glow exclusively by the potential necessary to operate the tube, the higher voltage being used merely for starting purposes, so that even with lower voltages a large current density is produced.

In the drawing attached to and forming a part of this specification several embodiments of the invention are shown for purposes of illustration in which- Fig. 1 is a side elevational view part1? in section of a container of a discharge device having therein one embodiment of the new and novel electrode shown in section.

Fig. 2 is a side elevational view of a stem of the container shown in Fig. 1 showing in section an alternative embodiment of the new and novel electrode sealed therein.

'g. 3 is the same as Fig. 2 showing another embodiment of the new and novel electrode in side elevation. t

Fig. 4 is'the same as- Fig. 3 showing another embodiment of the new and novel invention.

Fig. 5 is a side elevational view of the stem partly in section and of another embodiment of the invention entirely in section.

Fig. 6 is a side elevational view of the stem with another embodiment of the new and novel electrode shown'in section.

Like numbers denote like parts in all views of the invention.

Referring to Fig. 1 container I may be of ordinary glass or of glass which transmits ultra violet radiation such as quartz. Said container I may have any desired gaseous filling such as rare gas, common gas, mixtures of these gases with each other or with a vaporizable metal such as mercury. At each end of the container l is a stem 2 in which is sealed 9, current lead 3. A metal shell 4 is connected to said current lead 3 having therein a body 501 electron emitting oxide material in the form of a plug said material being a poor electrical conductor in its cold condition. Said oxide body may be set into shell 4 either firmly or with slight play as desired. The method of making oxide body 5 is by pressing and sintering the pulverized form of the oxide or silicate of alkalies, alkali earths, or rare earths. Suitable materials are, for example, the oxide or silicates of potassium, sodium, caesium, rubidium, calcium, barium, strontium, thorium, cerium, lanthanum and didymium. Oxide body 5 is notentirely covered by shell 4 but the end parts thereof extend beyond the rim of the shell into the discharge path. The discharge path forms first between metal shells 4 connected to the current circuit of the discharge device, heating said shells 4 until they glow. By radiation and conduction of the heat developed in the shells 4 the parts of the oxide body 5 adjacent the rimlof metal shell 4 are brought to an electron emitting condition and send out a strong stream of electrons which supports the arc. The large bulk of oxide body 5 is a reserve of electron emitting material. If, in the course of time, the oxide body 5 becomes pitted at its electron emitting parts adjacent the metal shell 4 and said parts are not heated other parts adjacent said shell 4 become electron emitting to support the discharge.

In the embodiment shown in Fig. 2, the electron emitting oxide body 5 is attached to the interior end of the current lead 3. The back part of the rod or peg shaped oxide body 5 is provided with a thin sprayed metal layer 6, which is connected to current lead 3. p

In the embodiment shown in Fig. 3 a rod shaped electron emitting oxide body 5 is used, placed at right angles to the discharge path, enclosed by a wire net I, and kept therein by friction. The wire net I and therewith the oxide body 5 is supported by two wires 8 which are connected to the same current lead 3.

The electrode shown in Fig. 4 consists of a rod shaped oxide body 5, straight or curved, as

desired, which is surrounded by a wire coil 9. The supports 8 of the wire winding and therewith the set-in oxide body 5 are again connected to a single current lead 3.

In the embodiment shown in Fig. 5 the current lead 3 extends through a plug shaped body 5 and in this case the front end It of said lead 3 extends on through the front surface of oxide body 5. The front end ID of the current lead 3 forms a metal coating, so that when the wire end It is brought to a glow by the current the heating of the surface part of the body 5 is v effected. If the oxide body 5 and the back part of the current lead 3 is enclosed in a shell ll consisting of heat resisting materialsuch as quartz or magnesium oxide, said oxide body 5 emits electrons better and the discharge is prevented from attaching to lead wire 3 located between the body 5 and the pinch part of the stem 2. Said shell H fits snugly into an off-set tube 12 of stem 2.

In the embodiment shown in Fig. 6 three wires l3, I4, l5 pierce a slab shaped electron emitting oxide body 5, said lead wires l3, I4, l5 are connected to the same current lead 3 in the interior of stem 2. The ends [3, l4 and I5 of the wires l3, l4, I5 extend beyond, and are bent over the surface of body 5 to facilitate the heating of body 5. Shell I6, which slips over the stem 2 and seats against a ring ll of the latter, is used in this case as the guard of the back part of the wires l3, I4, 15.

The electron emitting body shown in Figs. 5 and 6 are held in place by the tension exerted by wires I3, l4, IS. The supporting wires may also be pressed in the pulverized form of the electron emitting substance with their ends extending beyond the surface thereof. When the sintering takes place a good supporting joint between the support wire and the body 5 is made.

The new electrode may be used in the arts generally and particularly in electric light tubes and in rectifiers.

While we have shown, described and have pointed out in the annexed claims certain new and novel features of the invention it will be understood that various omissions, substitutions and changes in the forms and details thereof may be made by those skilled in the art without departing from the broad spirit and scope of the invention.

This application is a division of our co-pending application, Serial Number 447,051, filed April 24, 1930.

What we claim as new and desire to secure by Letters Patent of the United States, is:

1. An electric discharge device comprising a container, electrodes sealed therein, a filling of gas therein, one of said electrodes being a self heating one and comprising a rod shaped compact body of an oxide material having high electron emissivity characteristics and a metal body being a wire coil containing said compact body and partially covering the surface thereof and when cold supporting a starting discharge when the device is started into operation by the operating current applied across the main terminals of the device and supporting an are discharge in said device when said oxide has reached an electron emitting temperature, an electrical connection for said electrode, said electrical connection constituting a single inlead for said electrode.

2. A self heating thermionic cathode for an electric discharge device having high electron emissivity characteristics comprising a discharge supporting metal bddy'having a large surface as compared to its mass and supporting and partially covering the outer surface of an oxide body having high thermionic electron emissivity characteristics, a discharge supporting part of one of said bodies extending beyond the contiguous parts of said bodies, an electrical connection constituting a single inlead for said electrode, said electrode being a cold starting self heating one and having the property of passing large currents for long periods of time and remaining free from disintegration.

3. A self heating thermionic cathode for an electric discharge device having high electron emissivity characteristics comprising a discharge supporting metal body having a large surface as compared to its mass and supporting and partially covering the outer surface of an oxide body having high thermionic electron emissivity characteristics, a discharge supporting part of one of said bodies extending beyond the contiguous parts of said bodies, an electrical connection constituting a single inlead for said electrode, said electrode being a coldstarting one and having the property of passing large currents for long periods of time, remaining free from disintegration and being inert with respect to rare and common gas filling of said device.

4. A self heating thermionic cathode for gaseous electric discharge devices comprising a metallic conductor having a large surface as compared to its mass and supporting an oxide connection'constituting a single inlead for said electrode, said electrode structure when heated by the current of operation of the device having high thermionic electron emission and being free from disintegration by electric bombardment and from clean-up effects on the gas filling of the device.

5. A self heating thermionic cathode for electric discharge devices comprising a metallic conductor having a large surface as compared to its mass and supporting an oxide body of electron emissive material and extending along the outer surface thereof, said conductor being exposed in part to the discharge in the device and supporting a starting discharge when cold, a discharge supporting part of one of the elements of said electrode extending beyond the contiguous parts of said elements, an electrical connection constituting a single inlead for said elect-rode, said electrode structure when heated by the current of operation of the device having high thermionic electron emission and being free from disintegra t-ion by electric bombardment and from clean-up effects on the remnant atmosphere of the'device.

GEORG GAIDIES. MAR/CELLO ,PIRANI. 

